1. Field of the Invention
This invention relates to a method and apparatus for transdermal communication, and more particularly, to a method and apparatus which allows an implanted device within a body to communicate through a plurality of layers to an externally placed control unit.
2. Discussion
Transdermal communication systems have been used in a wide variety of applications in which communication between an externally placed device and a device implanted within an organism's body (i.e., such as that of a human) was necessary. These systems normally utilized an implanted electrical coil which was electronically coupled to the implanted device. Another coil was then coupled to the externally placed device and was electronically excited so as to produce a signal which was modulated and was within the radio frequency range. This modulated signal passed through a plurality of skin layers associated with the body and was received by the implanted coil. This received signal usually contained a plurality of coded information and produced a magnetic field around the implanted coil which caused the coil to produce a current Which was used to power the implanted device and activate various auxiliary devices associated therewith or which was demodulated causing the coded information to be received by the implanted device. Other past embodiments have used a frequency shift keying (FSK) technique to transfer coded information from the external coil to the implanted device while utilizing a concomitant type of standard radio frequency shift keying modulation and demodulation circuitry.
Many of these past systems have suffered from significant drawbacks in that the implanted coils were usually physically large when compared to the surrounding elements contained within the body and thusly were frequently difficult to implant since in many cases, the required implantation area was quite small. In some cases damage was done, to the body, during implantation.
These past systems also suffered from transmission errors due to their analog designs and were very susceptible to component failure due to the complex circuitry associated with the necessary modulation and demodulation functions and to significant delays especially when used in conjunction with digitally based implanted devices.